I was wondering how I could change attributes of a Widget in a callback.

The use-case would be that a plugin has different modi, the first modus would require additional parameter and the second modus does not need any further input. So the the second modus should render the widgets for further inputs invisible or disable them to make clear, that these have no effect.

One thing that complicates matters is that it’s not guaranteed that the widgets for your parameters are always the same. They change depending on the UI the Context currently uses. Furthermore, if ImageJ is running headless, there are no widgets.